Hair dye might just become a thing of the past when it comes to the battle against grays.
According to a European study,

Most scientists believe that buildup of hydrogen peroxide is responsible for the formation of gray hair. When we are young, the enzyme called catalase breaks down hydrogen peroxide in our hair, but as we age, we produce less catalase to counteract the accumulation of hydrogen peroxide.

Scientists in Europe are now developing a topical, ultraviolet B-activated pseudo-catalase product called PC-KUS to reverse gray hair.